Friday, July 22, 2011

how to rewire hazard lights to work with ignition off on

Hazard Lights

The usefullness of hazard lights is obvious and it's disappointing that bike chose not to put them on these bikes. The theory of them is simple, simply have a switch that connects the left and right indicators together and power the flasher unit regardless of the bike's ignition being on. There's a few "black boxes" on the market to put hazard lights on bikes. Most of them're in the US$60 price range, some have funky features like auto-shutdown or "wig wag" lights, but really all you need is something that'll make all your turn signals flash simultaneously, right? There's a few design issues to consider with this system.

  • The standard flasher unit's only rated to handle two lamps. If you put four lamps through it (or six if like me you have a trailer) you'll kill it in no time flat. You'll need to replace it with a heavy duty flasher suitable for use with hazard lights. If you have LED's in your indicators you'll need one that's not load sensitive, or you'll need to use load balancers on the LED's.
  • The hazard lights need to work when the ignition's off, but simply supplying power to the flasher when the ignition's off will allow power to feed back to the fuse box making various parts of the bike live when they're not supposed to be. Two solutions are to switch the normal power line to the flasher off when the new one's turned on, or to put a diode in the normal power line. I chose the diode as it was a lot simpler than extending wires to reach to the switch.
  • Simply connecting the left and right indicators together will stop them working in normal circumstances - ALL of them will flash when you signal left or right. Solution here's similar to the above, two diodes to stop them feeding back to each other when hazard's not selected.
  • Bikes aren't waterproof, electricity LIKES water, and most switches aren't sealed. You can either mount the switch in a sealed enclosure which makes for lots of bulk, or use a sealed switch. Jaycar Electronics stocks a suitable unit (part number ST0555) and for extra safety a rubber boot ((ST0590).
  • For safety the hazard lights must be fused. You can either run a seperate line to the battery with it's own fuse, or use the connector for the auxilliary power socket which is already fused (assuming you don't already have the aux power socket installed).
  • For legal and logical reasons you need a "pilot light" (read idiot light) for the hazard lights. The standard pilot light works by earthing through the opposite side's lamps but if both sides are flashing the pilot won't light. Two more diodes are used here, with both sides connected through them to one side of the lamp, and the other side earthed. You could use a seperate light (eg: an illuminated switch) if you want, if so you don't need to modify the standard one.

What you'll need

  • Heavy duty flasher (or Suitable LED flasher). There's several types so be sure you get the right one. This bike requires a three pin flasher, with pins marked 31, 49, and 49A. It also has to be a square one (not round) or it won't fit.
  • 5 power diodes, 1N4004 or similar (or 3 if you don't want to modify the idiot light)
  • DPST switch (most dual pole switches are also dual throw (DPDT), that's fine - we just ignore the second throw)
  • Various consumables eg: a metre or two of suitable gauge hookup wire, solder and iron, heatshrink tubing, PVC tape, zip ties.
  • The normal tools (8mm & 12mm spanners, 5mm allen key, wire cutters & strippers etc)

How it works

A flasher unit works by always having power supplied to the unit while the bike's on, and earthing the flasher through the lamps on one side or the other as selected by the indicator switch which causes the selected lamps to light. What our modification does is add a switch that does two things: supplies power to the flasher even when the bike's turned off, and connects both the left and right lamps to the flasher so it earths through all of them at once. It also adds five diodes to do three things: one diode to stop the fusebox being powered when the hazard lights are enabled, two diodes to stop the left and right sides feeding back to each other under normal circumstances, and two diodes to enable the pilot light to work when hazards are enabled. The original and modified circuit diagrams are shown below.

How it's built

Firstly you need to remove the following from your bike: both seats, tank console, fuel tank, wiring cover below front seat, battery box lid and cover (if fitted). The console can remain connected and slung over the handlebars. Remember to place the tank on something soft to avoid damage to the finish (a flattened cardboard box works fine). Located the flasher unit on the right side of the frame as shown below. Unplug it and replace it with your new one. You can turn the ignition on and make sure it works as normal if you like. (Don't start the bike though.)


I know bikes instructions tell you to do that when you're doing things like fitting windscreens and sissybars, but on this project we're messing with permanantly live connections so we actually have to do it this time.

The next step is to make up the switch. Below's a pic with the wiring layout for the switch and flasher unit. I'm assuming you're using a DPDT (dual pole dual throw) toggle switch. If you've chosen something else it shouldn't be too hard to interpret. The terminals on the switch probably aren't actually numbered, that's just for our reference. Note that all solder joints are also heatshrinked. Firstly solder about six inches of wire to terminals 1, 4 and 5. If you're using the aux power socket's connector you can crimp on a male spade lug to the end of terminal 4's wire, or if you're connecting to the battery use the inline fuse holder and solder a large ring lug onto the other end to connect to the positive battery terminal. Solder about two inches of wire to terminal 2, then solder the two diodes to the wire be careful about the polarity of the diodes). Solder about 15 inches of wire to the other end of each diode. If you want to add black sleeving to the two long wires and the wires to the flasher unit it makes for a neater installation, but it's not critical. It's also not a bad idea to insulate the unused terminals on the switch with a little heatshrink, melted and crimped at the open end. You might have to add some solder to those terminals to make them large enough for the heatshrink to grip.

Mount the switch in the engine support bracket from the left side. Feed the two wires from terminals 1 and 5 out to the base of the flasher unit, the wire from terminal 4 near the connector or battery, and the two wires from terminal 2 to the wiring harness below the seat. Do not connect power wires at this point. Try to run the wires along existing wires, you can add zip ties to keep them in place but don't fully tighten them yet - you'll want to adjust it all when you're done.

Next, locate the wiring harness below the front seat. You're looking for the harness that feeds the tail light and rear indicators. It has five wires, the colours of which change as they cross the connector. This is the point where we'll be feeding the output from the flasher back into the lights. You can use the wire on either side of the connector, but there's probably more free space on the "taillight side" of the connector. I unplugged it and pulled the harness out from the side of the rear guard, pulled back the black sleeving and cut, soldered and heatshrink'd the extra wires in there, then put it all back. This makes for a nice neat addition without adding extra bulk below the (already full) wiring cover.

"Bike Side" of connector
Taillight side of connector
Green/White Trace
Right Indicator
Green/Purple Trace
Brake Light
Tail Light
Green/Red Trace
Left Indicator

The next step is to modify the wiring at the flasher. Cut the wire leading to terminal 49 of the flasher about half way along it's free length. Solder the diode (noting its polarity) and the wire from terminal 5 of the switch to the socket, then solder the cut wire to the other end of the diode. Cut the wire from terminal 49A and splice in the wire from terminal 1 on the switch. You can now plug the power line into the socket (or onto the battery terminal as per your installation method). Connect the negative terminal of the battery and switch your hazard lights on. If it is all correct you should see all 4 lights flashing merrily away, however the pilot light won't be working at this point.. If they don't, or if you see smoke, you should disconnect it immediatley and retrace all your connections. Pay particular attention to the orientation of the diodes, as having them backwards will stop the working. (They can simply be turned around if you've put them in backwards, they won't be damaged.)

In the tank console locate the indicator pilot light, and cut both wires to it about half way along their free length. Solder a diode to each of these wires, then solder both diodes to one of the wires in the pilot light. Locate the (black) earth wire for the tacho/clock connector. Splice a wire into it, then solder that wire to the free wire on the pilot light. Insulate all connections as usual. Note: The wiring that bike have used in the tank console's wiring harness is of a type that doesn't take well to solder. It CAN be done by scratching the enamel off the individual strands and making sure the soldered joint is VERY hot, but it's a lot easier in this area to use "scotchlock" joiners or similar. Obviously this won't work with the diodes, however you can solder a short piece of normal wire to the diode then scotchlock that wire into the harness. I'm not happy with this method and am working on replacing the entire console harness with something a little more user-friendly, since I've made many modifications to this area and it's starting to get a little untidy. The picture below shows the diodes and eath connected to the back of the pilot light. Note the orientation of the diodes.


Test the hazard lights. All four corners should flash with the ignition on OR off, and the indicator switch in any position. The pilot light should also flash with both the hazards and indicators. If all's as it should be, reassemble your bike.

No comments:

Post a Comment